In recent years, a large number of solar power generation systems have been built as systems that effectively use renewable energy. Accordingly, reports of fire accidents caused by arc failure in the solar power generation systems are also increasing.
In a solar power generation system, it is necessary to rapidly shut off a circuit in order to prevent a fire from occurring due to an arc when the arc occurs. Therefore, a solar power generation system includes an arc detecting device that detects generation of an arc in the system.
In a solar power generation system that includes a solar cell string and is connected to a power conditioner (also referred to as a power conditioning system (PCS)), noise caused by an arc is generated when an arc which is a serial arc or a parallel arc is generated. In this case, a signal in which the noise caused by the arc is superimposed on switching noise of the power conditioner is generated in an output line of the solar cell string (a direct current power supply). Therefore, the arc detecting device acquires the signal of the output line, acquires a signal of the arc from the signal, and detects the generation of the arc.
For this type of arc detecting device, configurations disclosed in Patent Literatures 1 and 2 are known. In the configuration disclosed in Patent Literature 1, in a solar power generation system connected to a power conditioner, a current flowing through the solar power generation system is detected, a power spectrum of the detected current is obtained, and an electric arc is detected from the obtained power spectrum.
Meanwhile, in the configuration disclosed in Patent Literature 2, an arc is detected using a power spectrum of a voltage rather than a power spectrum of a current flowing through an output line of a solar cell string.